The detection of military high explosives and illicit drugs presents problems of paramount importance in the fields of counter terrorism and criminal investigation. Effectively dealing with such threats requires hand-portable, mobile and affordable instruments. The paper shows that solid-state gas sensors can contribute to the development of such instruments provided the sensors are incorporated into integrated sensor systems, which acquire the target substances in the form of particle residue from suspect objects and which process the collected residue through a sequence of particle sampling, solid-vapor conversion, vapor detection and signal treatment steps. Considering sensor systems with metal oxide gas sensors at the backend, it is demonstrated that significant gains in sensitivity, selectivity and speed of response can be attained when the threat substances are sampled in particle as opposed to vapor form.
Current‐voltage characteristics for the reduction of oxygen at silver and alloy electrodes formed with silver and elements having oxides of low electron affinity were studied in pre‐electrolyzed and in ordinary 15%
KOH
solution. In impure solutions or at the alloy electrodes straight Tafel lines were obtained, but with pure silver in pure solutions no such behavior was found. This is taken to indicate a dynamic surface of varying catalytic activity. With silver‐magnesium oxide surfaces, a potential about 100 mv higher than with pure silver was obtained at open circuit as well as under current drain. The possible mechanistic significance of the results is discussed in terms of the physical properties of the material and the behavior of the constituents in gas‐solid reactions.
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